Temperature discriminating dual igniter rocket ignition system

ABSTRACT

An igniter system for solid propellant type rockets and is designed to ignite the propellant over a wide range of temperature conditions. The system consists of a pair of igniters in circuitry with a power source. A thermostatic switch in the firing circuit acts upon a low temperature condition to permit firing of both igniters and upon high temperature, only one igniter.

mted States Patent 1 1 1111 3,73L629 Lombardi 1 1 May 8, 1973 [54]TEMPERATURE DISCRIMINATING [56] References Cited D AL IGNITER ROCKET INITION SSSTEM G UNITED STATES PATENTS 2,685,837 8/1954 Sage etal.102/702 A [75] Invent g Rmkaway, 3,287,912 11/1966 Wehlow eta] ..60/256[73] Assignee: The United States of America as Primary pendegl'assrepresented by the Secretary of the Anomey'doselah W" Army, Washington,D.C. CT 22 Filed: Jan. 27, 1971 An igniter system for sol1d propellanttype rockets and PP 110,286 is designed to ignite the propellant over awide range of temperature conditions. The system consists of a pair ofigniters in circuitry with a power source. A thermostatic switch in thefiring circuit acts p a 58 m d 7 70 2 A low temperature condition topermit firing of both i e 0 66/256 niters and upon high temperature,only one igniter.

2 Claims, 3 Drawing Figures Power aaurce l6 PATENTEDHAY ems I mvENTorgCharles /-7. Lombardi w; WJWM M J" '7 r9 5:, ATTORNEYS,

Power daurce l6 TEMPERATURE DISCRIMINATING DUAL IGNITER ROCKET IGNITIONSYSTEM The invention described herein may be manufac tured, used, andlicensed by or for the Government for governmental purposes without thepayment to me of any royalty thereon.

This invention relates to a temperature discriminating dual igniterrocket system and more particularly to a means of igniting a solidrocket propellant over a wide range of temperature conditions.

Solid propellant rocket motors are easiest to ignite at elevatedtemperatures and hardest to ignite at low temperatures, the output ofthe igniter being greater at tion characteristics over a very wide rangeof tempera-- ture, as for instance, 40 to +145 F. This was principallydue to the fact that the rocket systems had but one fixed charge whichwas expected to ignite the rocket motor under all temperatureconditions.

The present invention is designed to overcome the I aforesaid problemsin solid propellant ignition by using an incremental igniter, part ofwhich is suitable for high temperature operation while another part,which is initiated at the discretion of a temperature sensing device,when added to the first, makes up a total output.

that is suitable for low temperature operation.

It is therefore a principal object of this invention to provide a meansfor the ignition of a solid propellant rocket motor whereby a uniformignition output is achieved over a wide range of temperature conditions.

Another object is to provide a two-part igniter, one part suitable toignite the propellant at high temperature and the other part, when addedto the first part, the system is capable of igniting the propellant atlow temperatures.

A still further object is to provide a temperature sensing means in thefiring circuit of a two-part ignition system for a solid propellantrocket motor whereby one or both parts may be fired as the temperatureconditions require.

These and other objects and advantages of the present invention will befully apparent from the following description when taken in connectionwith the annexed drawing, in which:

FIG. 1 is an elevational view, partly in section, illustrating a solidpropellant missile and showing a dual ignition firing system constructedin accordance with this invention;

FIG. 2 is an elevational view ofa twin ignition system having a modifiedfiring circuit, and,

FIG. 3 is an axial section ofone ofthe igniters.

With reference in detail to the drawing in which like reference numeralsindicate like parts throughout the several views, reference character 1designates generally, a solid propellant type missile adapted to befired from a launching tube, not shown. Missile 1 includes a case 2having an ogive portion 3 and a cap 4 at its breech end. A payloadcharge is indicated by 5. Other components include blast nozzles 6supported by an aft bulkhead 7. Missile l is shown by way of exampleonly since other types of missiles could be used with this invention asis expedient.

A rocket motor is shown in the breech portion of missile l and consistsof a solid grain propellant 8 supported in case 2 by retaining elements9 and 10.

The ignition system of this invention, FIG. 1, is indicated generally by11 and consists of twin igniters 12 and 13 which are supported bysuitable means, not shown, in propellant grain 8, as shown in FIG. 1only.

A firing circuit for firing the igniters l2 and 13 is shown in FIG. 1and consists of leads 14 and 15 connected to a power source 16 and toigniter 12. Leads 17 and 18 connect leads 14 and 15 with igniter 13,there being shown a resistor 19 in lead 18. A temperature sensing device20, which may be a thermostatic switch, bridges lead 15 and 18.

The operation of the ignition system shown in FIG. 1 is as follows:

When the missile system is in the low temperature region, thermostaticswitch is open and both igniters l2 and 13 will be fired through leads14, 18, 15 and 17 from power source 16.

When the temperature of the system is sufficiently high so that bothigniters, when fired, would produce too great an output, thenthermostatic switch 20 would close, thus attenuating the electricalenergy directed to igniter l3 and permitting only igniter. 12 to firewhich would be sufficient to ignite the rocket motors solid propellantgrain 8. This arrangement of the firing cir cuit insures automaticfunctioning of the system.

An alternative firing system is shown in FIG. 2. In this system igniter12 is arranged to always function, it being connected directly to leadsl4 and 15 and power source 16. lgniter 13 is connected to leads 14 and15 through leads 17 and 18. Thermostatic switch 20 is positioned in lead18 and is normally closed at low temperature, but will open at acritical temperature, remaining open at high temperature. When themissile temperature is below the critical point, thermostatic switch 20is closed, allowing the current in the firing circuit to flow to bothigniters 12 and 13. At temperatures above the critical point,thermostatic switch 20 is open, blocking current from passing to igniter13, thus permitting only igniter 12 to fire.

In FIG. 3 there is illustrated one of the igniters, which are identicalin construction. Each igniter comprises a container fixed to a headassembly 22. A firing squib 23 connected to firing leads 24 is carriedby the head assembly. A primer charge 25 is retained in head assembly 22by a disc 26. A main charge 27 is disposed in container 21 and heldtherein by supports 28 and 29. Gas relief holes 30 are closed by aplastic wrap 31 so that when only one igniter is to be fired, hotcombustion gases from the fired igniter cannot enter the igniter notbeing used to prevent its firing also and prevent its cook off.

Operation of missile 1, shown in FIG. 1, is as follows: The missile l isplaced in a launching tube, not shown.

When one, or both igniters l2 and 13 are fired, propel- It is apparentfrom the foregoing that a highly efficient means for igniting a solidpropellant rocket charge has been achieved by the present invention.

What is claimed is:

1. In combination with a missile:

a propellant motor comprising a. a casing b. a hollow propellant grainin said casing;

c. a plurality of elongated igniters laterally spaced from each otherand housed completely within the interior space of said propellant grainin parallel relation to the longitudinal axis of said propellant grain;each of said igniters having a casing, an igniting charge within saidcasing, a pair of electrical leads, and means for preventingnon-electrical ignition of said igniting charge;

(I. a firing circuit for electrically igniting one of said igniters; and

e. at least one supplemental firing circuit for electrically igniting atleast one other of said igniters, said supplemental firing circuit beingoperable only below a predetermined ambient temperature; whereby saidpropellant grain may be ignited by said first-named igniter when theambient temperature is not less than said predetermined temperature, andby a plurality of said igniters when the ambient temperature is belowsaid predetermined temperature.

2. In combination with a missile a propellant motor comprising a. acasing;

b. a solid hollow propellant grain in said casing;

c. a pair of elongated igniters laterally spaced from each other andhoused completely within the interior space of said propellant grain inparallel relation to the longitudinal axis of said propellant grain;each of said igniters having a casing, an igniting charge within saidcasing, a pair of electrical lead, and means for preventingnon-electrical ignition of said igniting charge;

d. a firing circuit for electrically igniting one of said igniters; and

e. a supplemental firing circuit for electrically igniting the otherigniter, said supplemental firing circuit being operable only below apredetermined ambient temperature; whereby said propellant grain may beignited by said first-named igniter when the ambient temperature is notless than said predetermined temperature, and by both igniters when theambient temperature is below said predetermined temperature.

1. In combination with a missile: a propellant motor comprising a. acasing b. a hollow propellant grain in said casing; c. a plurality ofelongated igniters laterally spaced from each other and housedcompletely within the interior space of said propellant grain inparallel relation to the longitudinal axis of said propellant grain;each of said igniters having a casing, an igniting charge within saidcasing, a pair of electrical leads, and means for preventingnon-electrical ignition of said igniting charge; d. a firing circuit forelectrically igniting one of said igniters; and e. at least onesupplemental firing circuit for electrically igniting at least one otherof said igniters, said supplemental firing circuit being operable onlybelow a predetermined ambient temperature; whereby said propellant grainmay be ignited by said firstnamed igniter when the ambient temperatureis not less than said predetermined temperature, and by a plurality ofsaid igniters when the ambient temperature is below said predeterminedtemperature.
 2. In combination with a missile a propellant motorcomprising a. a casing; b. a solid hollow propellant grain in saidcasing; c. a pair of elongated igniters laterally spaced from each otherand housed completely within the interior space of said propellant grainin parallel relation to the longitudinal axis of said propellant grain;each of said igniters having a casing, an igniting charge within saidcasing, a pair of electrical lead, and means for preventingnon-electrical ignition of said igniting charge; d. a firing circuit forelectrically igniting one of said igniters; and e. a supplemental firingcircuit for electrically igniting the other igniter, said supplementalfiring circuit being operable only below a predetermined ambienttemperature; whereby said propellant grain may be ignited by saidfirst-named igniter when the ambient temperature is not less than saidpredetermined temperature, and by both igniters when the ambienttemperature is below said predetermined temperature.